Surge Test

The term “surge test” is frequently used to designate surge voltage testing in German-speaking countries. This term, which comes from the English language, describes the only test method for detecting shorts between electromagnetic windings or insulation problems inside one or multiple windings on wound materials. Wound materials may be coils, stators, or transformers, for instance. When motors fail, problems with winding insulation are frequently to blame. Instead of a surge test, a high-voltage test is also sometimes incorrectly performed in order to detect these insulation issues and short circuits. A high-voltage test alone, however, is not sufficient, since this only tests the insulation against the earth / ground or between galvanically separated parts of the wound materials. In a surge test, in contrast, the winding and layer insulation within the wound materials is specifically tested.

How does a surge test work?

During a surge test, a surge capacitor connected in parallel to the winding to be tested is discharged suddenly. A sinusoidal damped oscillation is created in the oscillating circuit created between the testing device and the winding, and this oscillation has a certain characteristic. Even the smallest differences between the winding parameters will cause changes to the oscillation during the surge test, which will allow problem areas in electric motors or other wound materials to be reliably detected. At problem areas which do not cause a flashover, small glow discharges will occur (corona). These are also detectable. Frequently, the surge voltage testing device is also equipped with a partial discharge test for this purpose.